Analysis of the population structure of Anaplasma phagocytophilum using multilocus sequence typing

Anaplasma phagocytophilum in urban and peri-urban passerine birds in Ile-de-France

Wild animals in general, birds in particular, play a key role in transporting ticks and propagating tick-borne pathogens. Several studies have confirmed the infection of birds with Anaplasma phagocytophilum, with overall prevalence varying widely from country to country and/or study to study. This zoonotic bacterium, transmitted mainly by ticks of the genus Ixodes, is responsible for granulocytic anaplasmosis in humans (HGA) and domestic animals (cats, dogs, horses). The disease is also called tick-borne fever (TBF) in ruminants. Extremely rare in the USA, TBF is very common in Europe, where it causes economic losses in livestock. Conversely, HGA is well established in the USA whereas only a few less severe cases have been observed in Europe. Current typing techniques support the existence of multiple variants with differences in virulence/pathogenicity and tropism for certain tick and host species. However, epidemiological cycles remain difficult to characterize in Europe. Several studies describe a cycle apparently involving only birds in Europe, but no such study has been conducted in mainland France. Our objectives were to search for A. phagocytophilum in passerine birds in the Ile-de-France region and to explore their diversity using groEL and ankA gene typing and multilocus sequence typing (MLST). Various tissues (spleen, liver, and skin) were collected from cadavers of 680 passerines between March and December 2021. The presence of A. phagocytophilum was detected by qPCR Taqman targeting the msp2 gene. Three blackbirds (Turdus merula) were found positive, representing detection rates of 0.4 % in all birds tested and 3.3 % in blackbirds. The higher frequency of detection in blackbirds could be at least partially explained by their lifestyle, as they feed on the ground. Analysis of the results of groEL and ankA typing and MLST from positive blackbirds support the hypothesis that the avian A. phagocytophilum strains in Ile-de-France are distinct from those found in mammals, and that they form their own cluster in Europe.

Potential drivers of vector-borne pathogens in urban environments: European hedgehogs (Erinaceus europaeus) in the spotlight

Vector-borne diseases (VBDs) are considered as (re-)emerging, but information on the transmission cycles and wildlife reservoirs is often incomplete, particularly with regard to urban areas. The present study investigated blood samples from European hedgehogs (Erinaceus europaeus) presented at wildlife rehabilitation centres in the region of Hanover. Past exposure to B. burgdorferi sensu lato (s.l.) and tick-borne encephalitis virus (TBEV) was assessed by serological detection of antibodies, while current infections with Borrelia spp., Anaplasma phagocytophilum, Rickettsia spp., Neoehrlichia mikurensis, Bartonella spp., Babesia spp. and Spiroplasma ixodetis were investigated by (q)PCR. Of 539 hedgehogs tested for anti-Borrelia antibodies, 84.8% (457/539) were seropositive, with a higher seropositivity rate in adult than subadult animals, while anti-TBEV antibodies were detected in one animal only (0.2%; 1/526). By qPCR, 31.2% (168/539) of hedgehog blood samples were positive for Borrelia spp., 49.7% (261/525) for A. phagocytophilum, 13.0% (68/525) for Bartonella spp., 8.2% for S. ixodetis (43/525), 8.0% (42/525) for Rickettsia spp. and 1.3% (7/525) for Babesia spp., while N. mikurensis was not detected. While further differentiation of Borrelia spp. infections was not successful, 63.2% of the A. phagocytophilum infections were assigned to the zoonotic ecotype I and among Rickettsia spp. infections, 50.0% to R. helvetica by ecotype- or species-specific qPCR, respectively. Sequencing revealed the presence of a Rickettsia sp. closely related to Rickettsia felis in addition to a Bartonella sp. previously described from hedgehogs, as well as Babesia microti and Babesia venatorum. These findings show that hedgehogs from rehabilitation centres are valuable sources to identify One Health pathogens in urban areas. The hedgehogs are not only exposed to pathogens from fleas and ticks in urban areas, but they also act as potent amplifiers for these vectors and their pathogens, relevant for citizens and their pets.

Molecular investigation of Anaplasma phagocytophilum and related strains among sheep flocks from different parts of Türkiye; with a note of phylogenetic analyses of Anaplasma phagocytophilum- like 1

Anaplasma phagocytophilum is a vector-borne zoonotic pathogen and can infect various vertebrate hosts, especially cattle, sheep, goats, horses, and dogs. Molecular-based studies have revealed that the agent has a high genetic diversity and closely related strains circulate in hosts. In this study, 618 sheep blood samples obtained from different geographic regions of Türkiye were researched for A.phagocytophilum and related strains with PCR, RFLP, and DNA sequence analyses. The DNA of these pathogens was detected in 110 (17.79%) samples. RFLP assay showed that all positive samples were infected with A.phagocytophilum-like 1, whereas A.phagocytophilum-like 2 and A.phagocytophilum were not detected. Partial parts of 16 S rRNA gene of seven randomly selected positive samples were sequenced. The phylogenetic analyses of these isolates revealed that at least two A.phagocytophilum-like 1 isolates circulate among hosts in Türkiye and around the world. A.phagocytophilum-related strains have been reported in molecular-based studies over the last few years, but there is a lack of data on the vector competence, epidemiology, clinical symptoms, and genetic diversity of these pathogens. Therefore, large-scale molecular studies are still needed to obtain detailed data on the above-mentioned topics.

Strains of Anaplasma phagocytophilum from horses in Ohio are related to isolates from humans in the northeastern USA

IMPORTANCE

The tick-borne obligatory intracellular bacterium Anaplasma phagocytophilum infects humans as well as domesticated and wild animals, causing a febrile disease collectively called granulocytic anaplasmosis. The epidemiology and the host species specificity and zoonotic potential of A. phagocytophilum strains remain unclear. In this study, ankA (encoding ankyrin A) and p44 gene sequences of A. phagocytophilum were determined in clinical specimens from horses in Ohio and compared with those found in A. phagocytophilum strains from various hosts and geographic regions. With increasing numbers of seropositive horses, the study points out the unrecognized prevalence and uncharacterized strains of A. phagocytophilum infection in horses and the importance of A. phagocytophilum molecular testing for the prevention of equine and human granulocytic anaplasmosis.

Granulocytic anaplasmosis in cats from central Europe and molecular characterization of feline Anaplasma phagocytophilum strains by ankA gene, groEL gene and multilocus sequence typing

BACKGROUND

Anaplasma phagocytophilum is a Gram-negative obligate intracellular bacterium that replicates in neutrophil granulocytes. It is transmitted by ticks of the Ixodes ricinus complex and causes febrile illness called granulocytic anaplasmosis primarily in humans, horses, dogs, sheep, cattle and goats. In comparison, clinically apparent disease has been described rarely in cats especially compared to dogs and horses. It is currently unknown whether cats are less susceptible to A. phagocytophilum or whether granulocytic anaplasmosis might be underdiagnosed in cats.

METHODS

To address this question, we examined clinical signs and laboratory findings in seven A. phagocytophilum infected cats from Germany and Switzerland. We then genetically characterized feline A. phagocytophilum strains and compared them to those from other hosts showing clinically apparent disease. For this purpose, ankA-based, groEL-based and multilocus sequence typing (MLST) were applied. Furthermore, the concordance between these typing methods was assessed.

RESULTS

Fever, lethargy and anorexia were the most common clinical signs in cats suffering from granulocytic anaplasmosis. The most frequent laboratory finding was thrombocytopenia. All three typing methods consistently indicated that the A. phagocytophilum strains found infecting cats are the same as those that cause disease in humans, dogs and horses. In general, the three typing methods applied exhibited high concordance.

CONCLUSIONS

The genetic characterization of the feline A. phagocytophilum strains indicates that strain divergence is not the explanation for the fact that granulocytic anaplasmosis is much less frequently diagnosed in cats than in dogs and horses. Otherwise, it may be possible that cats are less susceptible to the same strains than dogs and horse are. However, due to the unspecific clinical signs, it should be considered that granulocytic anaplasmosis may be under-diagnosed in cats.

Genomic analyses indicate the North American Ap-ha variant of the tick-vectored bacterium Anaplasma phagocytophilum was introduced from Europe

BACKGROUND

Anaplasma phagocytophilum is a tick-vectored, obligately intracellular bacterium that infects a diversity of vertebrate hosts. In North America, the Ap-ha variant of A. phagocytophilum can cause dangerous infections in humans, whereas symptomatic human infections in Europe are rare. Conversely, the European host-generalist ecotype of A. phagocytophilum frequently causes illness in domestic ruminants while no comparable infections have been recorded from North America. Despite these differences in pathogenicity, the Ap-ha variant is closely aligned phylogenetically with the European host-generalist ecotype. Furthermore, North American populations of A. phagocytophilum are less genetically diverse than those in Europe. Taken together, these observations suggest that the North American Ap-ha variant may represent an introduced population of this bacterium.

METHODS

Data from publicly available whole genomes of A. phagocytophilum were used to compare phylogeographic patterns and the extent of genetic divergence between the North American Ap-ha variant and the European host-generalist ecotype.

RESULTS

The results confirm that North American Ap-ha samples are phylogenetically nested within the diversity of the European host-generalist ecotype, and that Ap-ha likely radiated within the last 100 years. As expected, the Ap-ha variant also exhibited relatively low genetic diversity levels compared to the European host-generalist ecotype. Finally, North American Ap-ha harbored significantly more derived alleles than the European host-generalist A. phagocytophilum population.

CONCLUSIONS

Collectively, these results support the hypothesis that the Ap-ha variant was recently introduced to North America from Europe and underwent a strong genetic bottleneck during this process (i.e. a 'founder event'). Adaptation to novel vectors may have also played a role in shaping genetic diversity and divergence patterns in these pathogenic bacteria. These findings have implications for future studies aimed at understanding evolutionary patterns and pathogenicity variation within A. phagocytophilum.

Host-pathogen associations revealed by genotyping of European strains of Anaplasma phagocytophilum to describe natural endemic cycles

BACKGROUND

The zoonotic intracellular alpha-proteobacterium Anaplasma phagocytophilum is a tick-transmitted pathogen. The associations between vertebrate reservoirs and vectors are described as wide-ranging, and it was previously shown that the pathogenicity of A. phagocytophilum differs depending on the combination of pathogen variant and infected host species. This leads to the question of whether there are variations in particular gene loci associated with different virulence. Therefore, this study aims at clarifying existing host-variant combinations and detecting possible reservoir hosts. To understand these interactions, a complex toolset for molecular epidemiology, phylogeny and network theory was applied.

METHODS

Sequences of up to four gene loci (msp4, msp2, groEL and 16S rRNA) were evaluated for different isolates from variable host species, including, for example, dogs, cattle and deer. Variant typing was conducted for each gene locus individually, and combinations of different gene loci were analysed to gain more detailed information about the genetic plasticity of A. phagocytophilum. Results were displayed as minimum spanning nets and correlation nets.

RESULTS

The highest diversity of variants for all gene loci was observed in roe deer. In cattle, a reduced number of variants for 16S rRNA [only 16S-20(W) and 16S-22(Y)] but multiple variants of msp4 and groEL were found. For dogs, two msp4 variants [m4-20 and m4-2(B/C)] were found to be linked to different variants of the other three gene loci, creating two main combinations of gene loci variants. Cattle are placed centrally in the minimum spanning net analyses, indicating a crucial role in the transmission cycles by possibly bridging the vector-wildlife cycle to infections of humans and domestic animals. The minimum spanning nets confirmed previously described epidemiological cycles of the bacterium in Europe, showing separation of variants originating from wildlife animals only and a set of variants shared by wild and domestic animals.

CONCLUSIONS

In this comprehensive study of 1280 sequences, we found a high number of gene variants only occurring in specific hosts. Additionally, different hosts show unique but also shared variant combinations. The use of our four gene loci expand the knowledge of host-pathogen interactions and may be a starting point to predict future spread and infection risks of A. phagocytophilum in Europe.

Anaplasma phagocytophilum Ecotype Analysis in Cattle from Great Britain

Anaplasma phagocytophilum (A. phagocytophilum) is the aetiological agent of tick-borne fever in cattle and sheep, and granulocytic anaplasmosis in human and dogs. Livestock, companion animal and human infections with A. phagocytophilum have been reported globally. Across England and Wales, two isolates (called ecotypes) have been reported in ticks. This study examined A. phagocytophilum isolates present in livestock and wildlife in Great Britain (GB), with a particular focus on cattle. Clinical submissions (EDTA blood) from cattle (n = 21) and sheep (n = 3) were received by APHA for tick-borne disease testing and the animals were confirmed to be infected with A. phagocytophilum using a PCR targeting the Msp2 gene. Further submissions from roe deer (n = 2), red deer (n = 2) and Ixodes ricinus ticks (n = 22) were also shown to be infected with A. phagocytophilum. Subsequent analysis using a nested PCR targeting the groEL gene and sequencing confirmed the presence of ecotype I in cattle, sheep, red deer and Ixodes ricinus, and ecotype II in roe deer and I. ricinus removed from deer carcasses. Despite the presence of two ecotypes, widely distributed in ticks from England and Wales, only ecotype I was detected in cattle in this study.

Role of invasive carnivores (Procyon lotor and Nyctereutes procyonoides) in epidemiology of vector-borne pathogens: molecular survey from the Czech Republic

BACKGROUND

Vector-borne pathogens (VBPs) are a major threat to humans, livestock and companion animals worldwide. The combined effect of climatic, socioeconomic and host composition changes favours the spread of the vectors, together with the expansion of invasive carnivores contributing to the spread of the pathogens. In Europe, the most widespread invasive species of carnivores are raccoons (Procyon lotor) and raccoon dogs (Nyctereutes procyonoides). This study focused on the detection of four major groups of VBPs namely Babesia, Hepatozoon, Anaplasma phagocytophilum and Bartonella in invasive and native carnivores in the Czech Republic, with the emphasis on the role of invasive carnivores in the eco-epidemiology of said VBPs.

METHODS

Spleen samples of 84 carnivores of eight species (Canis aureus, Canis lupus, Lynx lynx, P. lotor, Martes foina, Lutra lutra, Mustela erminea and N. procyonoides) were screened by combined nested PCR and sequencing for the above-mentioned VBPs targeting 18S rRNA and cytB in hemoprotozoa, groEL in A. phagocytophilum, and using multilocus genotyping in Bartonella spp. The species determination is supported by phylogenetic analysis inferred by the maximum likelihood method.

RESULTS

Out of 84 samples, 44% tested positive for at least one pathogen. Five different species of VBPs were detected in P. lotor, namely Bartonella canis, Hepatozoon canis, Hepatozoon martis, A. phagocytophilum and Bartonella sp. related to Bartonella washoensis. All C. lupus tested positive for H. canis and one for B. canis. Three VBPs (Hepatozoon silvestris, A. phagocytophilum and Bartonella taylorii) were detected in L. lynx for the first time. Babesia vulpes and yet undescribed species of Babesia, not previously detected in Europe, were found in N. procyonoides.

CONCLUSIONS

Wild carnivores in the Czech Republic are hosts of several VBPs with potential veterinary and public health risks. Among the studied carnivore species, the invasive raccoon is the most competent host. Raccoons are the only species in our study where all the major groups of studied pathogens were detected. None of the detected pathogen species were previously detected in these carnivores in North America, suggesting that raccoons adapted to local VBPs rather than introduced new ones. Babesia vulpes and one new, probably imported species of Babesia, were found in raccoon dogs.

The Role of Wild Boars in the Circulation of Tick-Borne Pathogens: The First Evidence of Rickettsia monacensis Presence

Most wild mammals can serve as hosts both for tick-borne pathogens (TBPs) and for the ticks themselves. Among these, wild boars, due to their large body size, habitat and life span, show high exposure to ticks and TBPs. These species are now one of the widest-ranging mammals in the world, as well as the most widespread suid. Despite the fact that certain local populations have been decimated by African swine fever (ASF), wild boars are still considered overabundant in most parts of the world, including Europe. Altogether, their long-life expectancy, large home ranges including migration, feeding and social behaviors, wide distribution, overabundance and increased chances of interactions with livestock or humans make them suitable sentinel species for general health threats, such as antimicrobial-resistant microorganisms, pollution and ASF geographical distribution, as well as for the distribution and abundance of hard ticks and also for certain TBPs, such as Anaplasma phagocytophilum. The aim of this study was to evaluate the presence of rickettsial agents in wild boars from two counties in Romania. Among 203 blood samples of wild boars (Sus scrofa ssp. attila) collected during 3 (2019-2022) hunting seasons (September-February), 15 were found positive for tick-borne pathogen DNA. Six wild boars were positive for A. phagocytophilum DNA presence and nine for Rickettsia spp. The identified rickettsial species were R. monacensis (six) and R. helvetica (three). No animal was positive either for Borrelia spp., Ehrlichia spp. or Babesia spp. To the best of our knowledge, this is the first report of R. monacensis in European wild boars, thus adding the third species from the SFG Rickettsia, in the epidemiology of which this wild species may have a role as a reservoir host.

Distant genetic variants of Anaplasma phagocytophilum from Ixodes ricinus attached to people

BACKGROUND

Although the tick-borne pathogen Anaplasma phagocytophilum is currently described as a single species, studies using genetic markers can distinguish groups of variants associated with different hosts, pathogenicity, zoonotic potential and biotic and geographic niches. The objective of our study was to investigate the genetic diversity of A. phagocytophilum and Ixodes ricinus ticks attached to people.

METHODS

In collaboration with a commercial diagnostic company, a total of 52 DNA samples were obtained from ticks that tested positive for A. phagocytophilum by quantitative PCR. The genetic profile of each sample was determined using the groEL and ankA genes. Identification of the tick species was confirmed by partial sequencing of the COI subunit and a portion of the TROSPA gene.

RESULTS

All 52 ticks were identified as I. ricinus. Two protocols of nested PCR amplifying 1293- and 407-bp fragments of groEL of A. phagocytophilum yielded amplicons of the expected size for all 52 samples. Among all sequences, we identified 10 unique genetic variants of groEL belonging to ecotype I and ecotype II. The analysis targeting ankA was successful in 46 of 52 ticks. Among all sequences, we identified 21 unique genetic variants phylogenetically belonging to three clusters.

CONCLUSIONS

Our results indicate that ticks attached to people harbor distant genetic variants of A. phagocytophilum, some of which are not recognized as zoonotic. Further studies are needed to determine the risk of human infection by genetic variants other than those designated as zoonotic.

Epidemiological Survey on Tick-Borne Pathogens with Zoonotic Potential in Dog Populations of Southern Ethiopia

Dogs are known to host several tick-borne pathogens with zoonotic potential; however, scant information is available on the epidemiology of these pathogens in low-income tropical countries and in particular in sub-Saharan Africa. With the aim of investigating a wide range of tick-borne pathogens (i.e., Rickettsia spp., Anaplasma spp., Erhlichia spp., Borrelia spp., Hepatozoon spp. and Babesia spp.), 273 blood samples were collected from dogs in selected districts of Ethiopia and analyzed by real-time and/or end-point PCR. The results of the study showed that Hepatozoon canis was the most prevalent pathogen (53.8%), followed by Anaplasma phagocythophilum (7.0%), Babesia canis rossi (3.3%), Ehrlichia canis (2.6%) and Anaplasma platys (2.2%). Furthermore, five samples tested positive for Borrelia spp., identified as Borrelia afzelii (n = 3) and Borrelia burgdorferi (n = 2), and two samples for Rickettsia spp., identified as Rickettsia conorii (n = 1) and Rickettsia monacensis (n = 1). The finding of Anaplasma phagocythophilum and different species of the genera Borrelia and Rickettsia with zoonotic potential was unexpected and alarming, and calls for further investigation on the roles of dogs and on the tick, species acting as vector in this specific context. Other pathogens (Hepatozoon canis, Babaesia canis rossi, Anaplasma platys, Ehrlichia canis) are already known to have an important impact on the dogs' health but have minor zoonotic potential as they were rarely or never reported in humans. Dogs from rural areas were found to be at higher risk for different pathogens, probably due to the presence of other wild canids in the same environment. The findings of the present study contribute to a better knowledge of the epidemiology of tick-borne pathogens, which is relevant to human and animal health.

The Biological and Ecological Features of Northbound Migratory Birds, Ticks, and Tick-Borne Microorganisms in the African-Western Palearctic

Identifying the species that act as hosts, vectors, and vehicles of vector-borne pathogens is vital for revealing the transmission cycles, dispersal mechanisms, and establishment of vector-borne pathogens in nature. Ticks are common vectors for pathogens causing human and animal diseases, and they transmit a greater variety of pathogenic agents than any other arthropod vector group. Ticks depend on the movements by their vertebrate hosts for their dispersal, and tick species with long feeding periods are more likely to be transported over long distances. Wild birds are commonly parasitized by ticks, and their migration patterns enable the long-distance range expansion of ticks. The African-Palearctic migration system is one of the world's largest migrations systems. African-Western Palearctic birds create natural links between the African, European, and Asian continents when they migrate biannually between breeding grounds in the Palearctic and wintering grounds in Africa and thereby connect different biomes. Climate is an important geographical determinant of ticks, and with global warming, the distribution range and abundance of ticks in the Western Palearctic may increase. The introduction of exotic ticks and their microorganisms into the Western Palearctic via avian vehicles might therefore pose a greater risk for the public and animal health in the future.

Demographic Expansions and the Emergence of Host Specialization in Genetically Distinct Ecotypes of the Tick-Transmitted Bacterium Anaplasma phagocytophilum

In Europe, genetically distinct ecotypes of the tick-vectored bacterium Anaplasma phagocytophilum circulate among mammals in three discrete enzootic cycles. To date, potential ecological factors that contributed to the emergence of these divergent ecotypes have been poorly studied. Here, we show that the ecotype that predominantly infects roe deer (Capreolus capreolus) is evolutionarily derived. Its divergence from a host generalist ancestor occurred after the last glacial maximum as mammal populations, including roe deer, recolonized the European mainland from southern refugia. We also provide evidence that this host specialist ecotype's effective population size (N_e) has tracked changes in the population of its roe deer host. Specifically, both host and bacterium have undergone substantial increases in N_e over the past 1,500 years. In contrast, we show that while it appears to have undergone a major population expansion starting ~3,500 years ago, in the past 500 years, the contemporary host generalist ecotype has experienced a substantial reduction in genetic diversity levels, possibly as a result of reduced opportunities for transmission between competent hosts. IMPORTANCE The findings of this study reveal specific events important for the evolution of host specialization in a naturally occurring, obligately intracellular bacterial pathogen. Specifically, they show that host range shifts and the emergence of host specialization may occur during periods of population growth in a generalist ancestor. Our results also demonstrate the close correlation between demographic patterns in host and pathogen for a specialist system. These findings have important relevance for understanding the evolution of host range diversity. They may inform future work on host range dynamics, and they provide insights for understanding the emergence of pathogens that have human and veterinary health implications.

Prevalence of Tick-Borne Pathogens in Questing Ixodes ricinus and Dermacentor reticulatus Ticks Collected from Recreational Areas in Northeastern Poland with Analysis of Environmental Factors

Ticks, such as Ixodes ricinus and Dermacentor reticulatus, act as vectors for multiple pathogens posing a threat to both human and animal health. As the process of urbanization is progressing, those arachnids are being more commonly encountered in urban surroundings. In total, 1112 I. ricinus (n = 842) and D. reticulatus (n = 270) ticks were collected from several sites, including recreational urban parks, located in Augustów and Białystok, Poland. Afterwards, the specimens were examined for the presence of Borrelia spp., Babesia spp., Anaplasma phagocytophilum, Rickettsia spp., Bartonella spp., and Coxiella burnetii using the PCR method. Overall obtained infection rate reached 22.4% (249/1112). In total, 26.7% (225/842) of I. ricinus was infected, namely with Borrelia spp. (25.2%; 212/842), Babesia spp. (2.0%; 17/842), and A. phagocytophilum (1.2%; 10/842). Among D. reticulatus ticks, 8.9% (24/270) were infected, specifically with Babesia spp. (7.0%; 19/270), A. phagocytophilum (1.1%; 3/270), and Borrelia burgdorferi s.l. (0.7%; 2/270). No specimen tested positively for Rickettsia spp., Bartonella spp., or Coxiella burnetii. Co-infections were detected in 14 specimens. Results obtained in this study confirm that I. ricinus and D. reticulatus ticks found within the study sites of northeastern Poland are infected with at least three pathogens. Evaluation of the prevalence of pathogens in ticks collected from urban environments provides valuable information, especially in light of the growing number of tick-borne infections in humans and domesticated animals.

Molecular Survey of Babesia spp. and Anaplasma phagocytophilum in Roe Deer from a Wildlife Rescue Center in Italy

Simple Summary

Roe deer, whose populations are increasing and expanding throughout Europe, are suitable hosts for the maintenance of a variety of infectious tick-vectored microorganisms, that can infect both animals and humans. In this study the presence of tick-transmitted pathogens was investigated in roe deer recovered by a wildlife rescue center based in Italy. This kind of samples represents a convenient material for investigations under several aspects for both animals and researchers. Notably, no live trapping or killing are required to obtain samples, as they are collected in the context of the rescue activities and aimed to frame the health status of the animal. The investigated blood samples showed high positive rates to typical roe deer-related microorganisms (such as Babesia capreoli), and to the zoonotic agent Babesia venatorum. Roe deer were also positive to Anaplasma phagocytophilum strains mainly considered apathogenic or limited to wild ungulates. The obtained results underline the importance of a constant investigation on circulating tick-borne pathogens in roe deer, and generally speaking, in wild animal species, due to their potential role as a key factor in the endemic cycle of important infectious agents for domestic and wild animals, as well as humans.

Abstract

Babesia ssp. and Anaplasma spp. are tick-borne microorganisms representing a possible health risk for domestic and wild animals, as well as humans. Roe deer serve as a suitable reservoir host for some species ascribed to Babesia spp. and Anaplasma phagocytophilum taxa, also due to its important role in the maintenance of large populations of Ixodes ricinus, the main tick vector of these pathogens in Europe. Roe deer populations have been recently expanding throughout Europe, namely in Italy. However, the collection of samples from free-ranging wild animals for diagnostic investigations often includes several practical issues. This problem can be overcome using samples provided by wildlife rescue centers making them available for investigations following routine analyses. The presence of Babesia spp. and Anaplasma spp. in blood samples of 43 roe deer rescued by a wildlife rescue center in Emilia-Romagna region (Italy) was molecularly investigated. PCR screening revealed the presence of at least one pathogen in 86.05% of the animals, while co-infection occurred in 18.92% of the tested individuals. Zoonotic Babesia venatorum was found in 6.98% of the samples, while Babesia capreoli and Anaplasma phagocytophilum were detected in 74.42% and in 20.93%, respectively. No hematological signs compatible with clinical anaplasmosis or piroplasmosis, as well as absence of intracellular circulating microorganisms in blood smears, were observed, suggesting asymptomatic infection in the tested animals. These results confirm the usefulness of wild rescued animals as convenient source of biological samples for tick-borne pathogens investigation and the role of roe deer as a key factor in the endemic cycle of Babesia species and A. phagocytophilum.

The Role of Peridomestic Animals in the Eco-Epidemiology of Anaplasma phagocytophilum

Anaplasma phagocytophilum is an important tick-borne zoonotic agent of human granulocytic anaplasmosis (HGA). In Europe, the Ixodes ticks are the main vector responsible for A. phagocytophilum transmission. A wide range of wild animals is involved in the circulation of this pathogen in the environment. Changes in populations of vertebrates living in different ecosystems impact the ecology of ticks and the epidemiology of tick-borne diseases. In this study, we investigated four species, Western European hedgehog (Erinaceus europaeus), northern white-breasted hedgehog (Erinaceus roumanicus), Eurasian red squirrel (Sciurus vulgaris), and the common blackbird (Turdus merula), to describe their role in the circulation of A. phagocytophilum in urban and periurban ecosystems. Ten different tissues were collected from cadavers of the four species, and blood and ear/skin samples from live blackbirds and hedgehogs. Using qPCR, we detected a high rate of A. phagocytophilum: Western European hedgehogs (96.4%), northern white-breasted hedgehogs (92.9%), Eurasian red squirrels (60%), and common blackbirds (33.8%). In the groEL gene, we found nine genotypes belonging to three ecotypes; seven of the genotypes are associated with HGA symptoms. Our findings underline the role of peridomestic animals in the ecology of A. phagocytophilum and indicate that cadavers are an important source of material for monitoring zoonotic pathogens. Concerning the high prevalence rate, all investigated species play an important role in the circulation of A. phagocytophilum in municipal areas; however, hedgehogs present the greatest anaplasmosis risk for humans. Common blackbirds and squirrels carry different A. phagocytophilum variants some of which are responsible for HGA.

Ecological and evolutionary perspectives on tick-borne pathogen co-infections

Tick-borne pathogen co-infections are common in nature. Co-infecting pathogens interact with each other and the tick microbiome, which influences individual pathogen fitness, and ultimately shapes virulence, infectivity, and transmission. In this review, we discuss how tick-borne pathogens are an ideal framework to study the evolutionary dynamics of co-infections. We highlight the importance of inter-species and intra-species interactions in vector-borne pathogen ecology and evolution. We also propose experimental evolution in tick cell lines as a method to directly test the impact of co-infections on pathogen evolution. Experimental evolution can simulate in real-time the long periods of time involved in within-vector pathogen interactions in nature, a major practical obstacle to cracking the influence of co-infections on pathogen evolution and ecology.

Occurrence and Identification of Ixodes ricinus Borne Pathogens in Northeastern Italy

In Europe, Ixodes ricinus is the main vector for tick-borne pathogens (TBPs), the most common tick species in Italy, particularly represented in pre-alpine and hilly northern areas. From 2011 to 2017, ticks were collected by dragging in Belluno province (northeast Italy) and analyzed by molecular techniques for TBP detection. Several species of Rickettsia spp. and Borrelia spp. Anaplaspa phagocitophilum, Neoerlichia mikurensis and Babesia venatorum, were found to be circulating in the study area carried by I. ricinus (n = 2668, all stages). Overall, 39.1% of screened pools were positive for at least one TBP, with a prevalence of 12.25% and 29.2% in immature stages and adults, respectively. Pathogens were detected in 85% of the monitored municipalities, moreover the presence of TBPs varied from one to seven different pathogens in the same year. The annual TBPs prevalence fluctuations observed in each municipality highlights the necessity of performing continuous tick surveillance. In conclusion, the observation of TBPs in ticks remains an efficient strategy for monitoring the circulation of tick-borne diseases (TBDs) in a specific area.

Detection of Anaplasma phagocytophilum in European brown hares (Lepus europaeus) using three different methods

European brown hare (Lepus europaeus Pallas 1778) is a broadly distributed lagomorph species in Europe, recognized as a host for Ixodes ricinus and reservoir of a wide range of pathogens with zoonotic potential. Even though Lepus europaeus represents an important game animal in Central Europe, the data available on Anaplasma phagocytophilum in this lagomorph are scarce. In this study, three populations of brown hare from distinct localities in the Czech Republic were analysed for the presence of Anaplasma phagocytophilum DNA. We used standard qPCR, targeting the msp2 gene and adapted the same assay also for digital droplet PCR. Out of 91 samples, these two methods identified 9 and 12 as positive, respectively. For taxonomic analysis, we amplified the groEL gene from five of six samples that were found positive by both methods. In phylogenetic analyses, this haplotype belongs to ecotype 1, and to the subclade with isolates from cervids and I. ricinus. Our findings underline the importance of correct result interpretation and positivity cut-off set-up for different detection methods of A. phagocytophilum. This bacterium is characterized by a high intraspecific variability and highly sensitive detection itself, is not enough. Detailed molecular typing is necessary to define the zoonotic potential of different strains and their natural reservoirs.

Epidemiological and Clinicopathological Features of Anaplasma phagocytophilum Infection in Dogs: A Systematic Review

Anaplasma phagocytophilum is a worldwide emerging zoonotic tick-borne pathogen transmitted by Ixodid ticks and naturally maintained in complex and incompletely assessed enzootic cycles. Several studies have demonstrated an extensive genetic variability with variable host tropisms and pathogenicity. However, the relationship between genetic diversity and modified pathogenicity is not yet understood. Because of their proximity to humans, dogs are potential sentinels for the transmission of vector-borne pathogens. Furthermore, the strong molecular similarity between human and canine isolates of A. phagocytophilum in Europe and the USA and the positive association in the distribution of human and canine cases in the USA emphasizes the epidemiological role of dogs. Anaplasma phagocytophilum infects and survives within neutrophils by disregulating neutrophil functions and evading specific immune responses. Moreover, the complex interaction between the bacterium and the infected host immune system contribute to induce inflammatory injuries. Canine granulocytic anaplasmosis is an acute febrile illness characterized by lethargy, inappetence, weight loss and musculoskeletal pain. Hematological and biochemistry profile modifications associated with this disease are unspecific and include thrombocytopenia, anemia, morulae within neutrophils and increased liver enzymes activity. Coinfections with other tick-borne pathogens (TBPs) may occur, especially with Borrelia burgdorferi, complicating the clinical presentation, diagnosis and response to treatment. Although clinical studies have been published in dogs, it remains unclear if several clinical signs and clinicopathological abnormalities can be related to this infection.

Development of a real-time PCR method for rapid diagnosis of canine babesiosis and anaplasmosis

Background

Canine babesiosis and anaplasmosis, caused by Babesia canis and Anaplasma phagocytophilum, respectively, are significant tick-borne diseases in Baltic countries. Both diseases can be diagnosed on the basis of clinicopathological findings, by direct pathogen detection in blood smears or by indirect pathogen detection; however, because of high selectivity and specificity, molecular methods may be advantageous. The goal of this study was to develop a duplex real-time polymerase chain reaction (RT-PCR) method for the detection of B. canis and A. phagocytophilum in canine clinical samples.

Methods

Sequence-based polymorphism analysis of genes encoding B. canis-specific merozoite surface protein Bc28.1 (Bc28.1) and A. phagocytophilum malate dehydrogenase (mdh) was performed on pathogen isolates present in Latvian domestic dogs. The obtained results were used to design a species-specific duplex RT-PCR assay.

Results

The presence of three B. canis Bc28.1 gene sequence types was revealed in canine samples with a nonuniform geographical distribution, and two types of A. phagocytophilum mdh genes were detected. The novel duplex RT-PCR assay provided correct classification of samples positive and negative for B. canis and A. phagocytophilum. The analytical sensitivity of this assay was ten gene copies/ reaction for both pathogens.

Conclusions

A novel duplex RT-PCR molecular method was developed for the detection of B. canis and A. phagocytophilum in canine clinical samples. Sequence variability of Bc28.1 and mdh genes indicated the genetic variability of B. canis and A. phagocytophilum isolates occurring in Latvian domestic dogs.

Graphic Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04756-9.

Genetic diversity of Anaplasma bacteria: Twenty years later

The genus Anaplasma (family Anaplasmataceae, order Rickettsiales) includes obligate intracellular alphaproteobacteria that multiply within membrane-bound vacuoles and are transmitted by Ixodidae ticks to vertebrate hosts. Since the last reclassification of Anaplasmataceae twenty years ago, two new Anaplasma species have been identified. To date, the genus includes eight Anaplasma species (A. phagocytophilum, A. marginale, A. centrale, A. ovis, A. bovis, A. platys, A. odocoilei, and A. capra) and a large number of unclassified genovariants that cannot be assigned to known species. Members of the genus can cause infection in humans and a wide range of domestic animals with different degrees of severity. Long-term persistence which, in some cases, is manifested as cyclic bacteremia has been demonstrated for several Anaplasma species. Zoonotic potential has been shown for A. phagocytophilum, the agent of human granulocytic anaplasmosis, and for some other Anaplasma spp. that suggests a broader medical relevance of this genus. Genetic diversity of Anaplasma spp. has been intensively studied in recent years, and it has been shown that some Anaplasma spp. can be considered as a complex of genetically distinct lineages differing by geography, vectors, and host tropism. The aim of this review was to summarize the current knowledge concerning the natural history, pathogenic properties, and genetic diversity of Anaplasma spp. and some unclassified genovariants with particular attention to their genetic characteristics. The high genetic variability of Anaplasma spp. prompted us to conduct a detailed phylogenetic analysis for different Anaplasma species and unclassified genovariants, which were included in this review. The genotyping of unclassified genovariants has led to the identification of at least four distinct clades that might be considered in future as new candidate species.

Molecular detection and identification of piroplasms (Babesia spp. and Theileria spp.) and Anaplasma phagocytophilum in questing ticks from northwest Spain

Anaplasma phagocytophilum and some piroplasm species are pathogens mainly transmitted by Ixodes ricinus. Considering that this tick species is predominant in north-western Spain, individual specimens (652 nymphs, 202 females and 202 males) and 23 larval pools were processed to determine the prevalence of these pathogens in questing I. ricinus from that region. Additionally, Dermacentor marginatus, Dermacentor reticulatus, Ixodes frontalis and Ixodes acuminatus were individually analysed. The groESL operon as well as the 16S rRNA and msp2 genes of Anaplasma were analysed. Similarly, piroplasms were identified at the 18S rRNA gene and the ITS1 of Babesia spp. and Theileria spp. Babesia venatorum (1.5%), A. phagocytophilum (0.7%), Babesia microti (0.3%) and Theileria sp. OT3 (0.2%) were detected in I. ricinus. A single I. frontalis (8.3%) tested positive to A. phagocytophilum. Although a low percentage of I. ricinus were infected with A. phagocytophilum and piroplasms, a potentially human pathogenic variant of A. phagocytophilum was detected, and both Babesia species found were zoonotic. Since the vector of Theileria sp. OT3 remains unknown, further investigations are needed to unravel the role of I. ricinus in the transmission of this piroplasm.

Anaplasma phagocytophilum and Babesia Species of Sympatric Roe Deer (Capreolus capreolus), Fallow Deer (Dama dama), Sika Deer (Cervus nippon) and Red Deer (Cervus elaphus) in Germany

(1) Background: Wild cervids play an important role in transmission cycles of tick-borne pathogens; however, investigations of tick-borne pathogens in sika deer in Germany are lacking. (2) Methods: Spleen tissue of 74 sympatric wild cervids (30 roe deer, 7 fallow deer, 22 sika deer, 15 red deer) and of 27 red deer from a farm from southeastern Germany were analyzed by molecular methods for the presence of Anaplasma phagocytophilum and Babesia species. (3) Results: Anaplasma phagocytophilum and Babesia DNA was demonstrated in 90.5% and 47.3% of the 74 combined wild cervids and 14.8% and 18.5% of the farmed deer, respectively. Twelve 16S rRNA variants of A. phagocytophilum were delineated. While the infection rate for A. phagocytophilum among the four cervid species was similar (71.4% to 100%), it varied significantly for Babesia between roe deer (73.3%), fallow deer (14.3%), sika deer (27.3%) and red deer (40.0%). Deer ≤2 years of age tested significantly more often positive than the older deer for both A. phagocytophilum and Babesia species. (4) Conclusions: This study confirms the widespread occurrence of A. phagocytophilum and Babesia species in wild cervids and farmed red deer in Germany and documents the co-occurrence of the two tick-borne pathogens in free-ranging sika deer.

Spotted fever group rickettsiae in Dermacentor marginatus from wild boars in Italy

Following the increase in wild boar population recorded in urban and peri-urban areas throughout Europe, the present survey aimed to assess the occurrence of zoonotic tick-borne pathogens (TBPs) in wild boars living in southern Italy and in their ticks for evaluating the potential risk of infection for animals and humans. From October to December 2019, a total of 176 ticks collected from 93 wild boars andtheir spleen samples were molecularly screened for selected TBPs. Overall, all the wild boars were infested by ticks (mean intensity, 1.9) with Dermacentor marginatus and Ixodes ricinus being identified in 99.4% and 0.6%, respectively. Out of 93 wild boars, 17 (18.3%) were infested by ticks which scored positive to spotted fever group (SFG) Rickettsia species. Rickettsia slovaca and Rickettsia raoultii were identified in 16 (9%) and 1 (0.6%) D. marginatus, respectively, whereas a single I. ricinus (0.6%) was infected by R. slovaca. A single wild boar (1.1%) tested positive to R. slovaca. All ticks and wild boars scored negative to Babesia/Theileria spp., Ehrlichia spp., Anaplasma spp., Candidatus Neoehrlichia spp., Coxiella burnetii and Borrelia burgdorferi sensu lato complex. Data herein obtained suggest that wild boars are involved in the maintenance of D. marginatus in the environment as in peri-urban areas herein investigated. An integrated management approach is advocated for wild boar population control and in preventing the potential risk of TBPs infection in animals and humans.

Wild boar as a potential reservoir of zoonotic tick-borne pathogens

The wild boar (Sus scrofa) population has increased dramatically over the last decades throughout Europe and it has become a serious pest. In addition, the common habitat of wild boar and of the tick, Ixodes ricinus, indicates the potential of wild boar to play a role in epidemiology of epizootic and zoonotic tick-borne pathogens, including Anaplasma phagocytophilum. In Europe, epidemiological cycles and reservoirs of A. phagocytophilum, including its zoonotic haplotypes, are poorly understood. In this study, we focused on detection and further genetic characterization of A. phagocytophilum and piroplasmids in 550 wild boars from eleven districts of Moravia and Silesia in the Czech Republic. Using highly sensitive nested PCR targeting the groEL gene, the DNA of A. phagocytophilum was detected in 28 wild boars (5.1 %) representing six unique haplotypes. The dominant haplotype was found in 21 samples from 7 different districts. All detected haplotypes clustered in the largest clade representing the European ecotype I and the dominant haplotype fell to the subclade with the European human cases and strains from dogs and horses. Nested PCR targeting the variable region of the 18S rRNA gene of piroplasmids resulted in one positive sample with 99.8 % sequence identity to Babesia divergens. The presence of these two pathogens that are primarily circulated by I. ricinus confirms the local participation of wild boar in the host spectrum of this tick and warrants experimental studies to address wild boar as a reservoir of zoonotic haplotypes of A. phagocytophilum.

Genetic variability of Anaplasmataceae circulating in small mammals and ticks in an Ixodes persulcatus/Ixodes trianguliceps sympatric area in Russian Siberia

A total of 705 rodents from Myodes, Microtus, and Apodemus genera, 396 adult questing Ixodes persulcatus, and 115 Ixodes larvae and nymphs taken from rodents (and then molted under laboratory conditions to nymphs and adults) were collected in 2013-2018 in Omsk province, Russian Siberia, and examined for the presence of Anaplasmataceae. DNA of Anaplasma phagocytophilum was detected in 29.5 % rodents, 3.8 % questing I. persulcatus, two molted adult I. persulcatus, and one molted adult Ixodes trianguliceps. Ehrlichia muris DNA was found in specimens from 12.1 % rodents, 3.0 % questing I. persulcatus, 14 % molted adult I. persulcatus, and one molted adult I. trianguliceps. Neoehrlichia mikurensis DNA was found in 0.6 % blood samples. It was suggested that in the studied area A. phagocytophilum and E. muris are mainly transmitted to small rodents by I. trianguliceps and I. persulcatus, respectively. Based on groEL gene sequence analysis, three phylogenetic clusters of A. phagocytophilum (clusters 4, 5, 6, according to Jaarsma et al., 2019) were identified. Most of genotyped A. phagocytophilum isolates obtained from rodents (87.6 %) and a single isolate found in a molted adult I. trianguliceps belonged to cluster 5. Cluster 6 contained 11.8 % genotyped specimens from rodents, and one questing and two molted adult I. persulcatus, while cluster 4 included specimens from 93 % genotyped questing I. persulcatus and one vole. The finding of A. phagocytophilum from clusters 5 and 6 in voles from the same sampling area indicated that clusters 5 and 6 segregate according to the tick-carriers, but not the geography. Most of the genotyped specimens of E. muris and N. mikurensis corresponded to typical genotypes detected in Asian Russia previously. In addition, new genetic variants of E. muris and N. mikurensis, which significantly differed from other known isolates and formed separate branches on phylogenetic trees, were identified in several voles.

The absence of the drhm gene is not a marker for human-pathogenicity in European Anaplasma phagocytophilum strains

BACKGROUND

Anaplasma phagocytophilum is a Gram-negative obligate intracellular bacterium that replicates in neutrophil granulocytes. It is transmitted by ticks of the Ixodes ricinus complex and causes febrile illness in humans and animals. The geographical distribution of A. phagocytophilum spans the Americas, Europe, Africa and Asia. However, human disease predominantly occurs in North America but is infrequently reported from Europe and Asia. In North American strains, the absence of the drhm gene has been proposed as marker for pathogenicity in humans whereas no information on the presence or absence of the drhm gene was available for A. phagocytophilum strains circulating in Europe. Therefore, we tested 511 European and 21 North American strains for the presence of drhm and compared the results to two other typing methods: multilocus sequence typing (MLST) and ankA-based typing.

RESULTS

Altogether, 99% (478/484) of the analyzable European and 19% (4/21) of the North American samples from different hosts were drhm-positive. Regarding the strains from human granulocytic anaplasmosis cases, 100% (35/35) of European origin were drhm-positive and 100% (14/14) of North American origin were drhm-negative. Human strains from North America and Europe were both part of MLST cluster 1. North American strains from humans belonged to ankA gene clusters 11 and 12 whereas European strains from humans were found in ankA gene cluster 1. However, the North American ankA gene clusters 11 and 12 were highly identical at the nucleotide level to the European cluster 1 with 97.4% and 95.2% of identity, respectively.

CONCLUSIONS

The absence of the drhm gene in A. phagocytophilum does not seem to be associated with pathogenicity for humans per se, because all 35 European strains of human origin were drhm-positive. The epidemiological differences between North America and Europe concerning the incidence of human A. phagocytophilum infection are not explained by strain divergence based on MLST and ankA gene-based typing.

Comparison of tick-borne pathogen prevalence in Ixodes ricinus ticks collected in urban areas of Europe

Tick-borne diseases are a major threat to human and animal health. An increasing number of natural habitats have been transformed into urban areas by human activity; hence, the number of reported tick bites in urban and suburban areas has risen. This retrospective analysis evaluated 53 scientific reports concerning infections of Ixodes ricinus ticks collected from urban and suburban areas of Europe between 1991 and 2017. The results indicate significant differences in many variables, including a higher number of Anaplasma phagocytophilum infections in Eastern Europe than in Western Europe. The opposite result was observed for Candidatus Neoehrlichia mikurensis infections. A comparison of climate zones revealed that Borrelia burgdorferi s.l. infections have the greatest median incidence rate in subtropical climate zones. No statistical significance was found when comparing other tick-borne pathogens (TBPs), such as Borrelia miyamotoi, Rickettsia spp., Babesia spp., Bartonella spp., Ehrlichia spp., Coxiella burnetii and Francisella tularensis. The analysis also showed significant differences in the overall prevalence of TBPs according to average temperatures and rainfall across Europe. This retrospective study contributes to the knowledge on the occurrence and prevalence of TBPs in urbanized areas of Europe and their dependence on the habitats and geographical distributions of ticks. Due to the increased risk of tick bites, it is of great importance to investigate infections in ticks from urban and suburban areas.

Co-infection, reinfection and superinfection with Anaplasma phagocytophilum strains in a cattle herd based on ankA gene and multilocus sequence typing

BACKGROUND

Anaplasma phagocytophilum is a Gram-negative obligate intracellular bacterium that replicates in neutrophil granulocytes. It is transmitted by ticks of the Ixodes ricinus complex and causes febrile illness in humans and animals. We used multilocus sequence typing (MLST) and ankA gene-based typing to study the molecular epidemiology of the A. phagocytophilum strains circulating in a German cattle herd over one pasture season. The aim was to investigate whether co-infection with two distinct variants, reinfection with the same and/or superinfection by a different strain occurred during one pasture season. Eight genetic loci were sequenced in 47 PCR-positive samples from 15 animals.

RESULTS

Five different sequence types (ST) and four ankA alleles were detected in the cattle herd. Three different ST caused clinically overt tick-borne fever in primary infected animals. The concordance between ST and ankA allele was 100%. Therefore, the housekeeping genes used for MLST and the highly variable ankA gene were concatenated to increase resolution. Co-infection could be proven because samples of chronologically close collection dates were included. Co-infecting A. phagocytophilum strains differed by 14 to 18 single nucleotide polymorphisms (SNPs). Most superinfecting variants varied by 14 SNPs from the previous strain and appeared in median after a free interval of 31 days. Thus, it is unlikely that superinfecting strains arose by in-animal evolution. Immunity against re- or superinfection was assumed because the cattle developed clinical signs only during primary infection.

CONCLUSIONS

The tick-pathogen-vertebrate host interaction is probably much more complex than previously thought taking into account the frequently occurring events of co-infection, reinfection and superinfection. This complex situation could not be easily simulated in an experimental infection and underlines the value of field studies.

A divergent Anaplasma phagocytophilum variant in an Ixodes tick from a migratory bird; Mediterranean basin

Anaplasma phagocytophilum (AP) has vast geographical and host ranges and causes disease in humans and domesticated animals. We investigated the role of northward migratory birds in the dispersal of tick-borne AP in the African-Western Palearctic.

Ticks were collected from northward migratory birds trapped during spring migration of 2010 at two localities in the central Mediterranean Sea. AP DNA was detected by PCR (gltA and 16S rRNA) and variant determination was performed using ankA sequences.

In total, 358 ticks were collected. One of 19 ticks determined as Ixodes was confirmed positive for AP DNA. The tick was collected from a woodchat shrike (Lanius senator senator) trapped in Greece, and molecularly determined to belong to the I. ricinus complex and sharing highest (95%) 16S RNA sequence identity to I. gibbosus. The ankA AP sequence exhibited highest similarity to sequences from rodents and shrews (82%) and ruminants (80%). Phylogenetic analyses placed it convincingly outside other clades, suggesting that it represents a novel AP variant.

The divergent Ixodes species harboring a novel AP variant could either indicate an enzootic cycle involving co-evolution with birds, or dissemination from other regions by avian migration. None of the 331 Hyalomma marginatum sensu lato ticks, all immature stages, were positive for AP DNA, lending no evidence for the involvement of Hyalomma ticks transported by birds in the ecology of AP.

Phylogeographical diversity of Anaplasma phagocytophilum in the Asian part of Russia based on multilocus sequence typing and analysis of the ankA gene

Anaplasma phagocytophilum is a tick-transmitted bacterium that replicates in neutrophil granulocytes and elicits febrile disease in humans and animals; it is widely distributed in the Americas, Europe, Africa, and Asia. A. phagocytophilum is commonly regarded as a single species, but several genetic variants with distinct host distribution and geographical origin have been described. In a previous study, we used multilocus sequence typing (MLST) to characterize 25 A. phagocytophilum strains from Ixodes spp. ticks collected in the Asian part of Russia. The obtained concatenated sequences formed two separate clades reflecting their Asiatic origin and/or the vector species. As one of the clades was related to A. phagocytophilum strains from European voles and shrews, we here extended our analysis to seven samples from the northern red-backed vole Myodes rutilus and included 38 additional strains of Asiatic origin from Ixodes persulcatus, I. pavlovskyi, and their hybrids. Further, the ankA gene was sequenced in 59 A. phagocytophilum strains from ticks and voles. The Russian strains belonged to the two new MLST clusters 5 (38/70) and 6 (32/70), previously referred to as clades within clusters 1 and 3, respectively. The total number of sequence types (STs) found was 27 including 12 new STs. The ankA sequences were unique and formed two new clusters: cluster 8 (34/59) and cluster 10 (25/59). The concordance between MLST and ankA-based typing was 100%. This means that at least two distinct genetic groups of A. phagocytophilum circulate in the Asian Part of Russia whose reservoir hosts and transmission cycles have to be further elucidated.

A review on the eco-epidemiology and clinical management of human granulocytic anaplasmosis and its agent in Europe

Anaplasma phagocytophilum is the agent of tick-borne fever, equine, canine and human granulocytic anaplasmosis. The common route of A. phagocytophilum transmission is through a tick bite, the main vector in Europe being Ixodes ricinus. Despite the apparently ubiquitous presence of the pathogen A. phagocytophilum in ticks and various wild and domestic animals from Europe, up to date published clinical cases of human granulocytic anaplasmosis (HGA) remain rare compared to the worldwide status. It is unclear if this reflects the epidemiological dynamics of the human infection in Europe or if the disease is underdiagnosed or underreported. Epidemiologic studies in Europe have suggested an increased occupational risk of infection for forestry workers, hunters, veterinarians, and farmers with a tick-bite history and living in endemic areas. Although the overall genetic diversity of A. phagocytophilum in Europe is higher than in the USA, the strains responsible for the human infections are related on both continents. However, the study of the genetic variability and assessment of the difference of pathogenicity and infectivity between strains to various hosts has been insufficiently explored to date. Most of the European HGA cases presented as a mild infection, common clinical signs being pyrexia, headache, myalgia and arthralgia. The diagnosis of HGA in the USA was recommended to be based on clinical signs and the patient’s history and later confirmed using specialized laboratory tests. However, in Europe since the majority of cases are presenting as mild infection, laboratory tests may be performed before the treatment in order to avoid antibiotic overuse. The drug of choice for HGA is doxycycline and because of potential for serious complication the treatment should be instituted on clinical suspicion alone.

Presence of Roe Deer Affects the Occurrence of Anaplasma phagocytophilum Ecotypes in Questing Ixodes ricinus in Different Habitat Types of Central Europe

The way in which European genetic variants of Anaplasma phagocytophilum circulate in their natural foci and which variants cause disease in humans or livestock remains thus far unclear. Red deer and roe deer are suggested to be reservoirs for some European A. phagocytophilum strains, and Ixodes ricinus is their principal vector. Based on groEL gene sequences, five A. phagocytophilum ecotypes have been identified. Ecotype I is associated with the broadest host range, including strains that cause disease in domestic animals and humans. Ecotype II is associated with roe deer and does not include zoonotic strains. In the present study, questing I. ricinus were collected in urban, pasture, and natural habitats in the Czech Republic, Germany, and Slovakia. A fragment of the msp2 gene of A. phagocytophilum was amplified by real-time PCR in DNA isolated from ticks. Positive samples were further analyzed by nested PCRs targeting fragments of the 16S rRNA and groEL genes, followed by sequencing. Samples were stratified according to the presence/absence of roe deer at the sampling sites. Geographic origin, habitat, and tick stage were also considered. The probability that A. phagocytophilum is a particular ecotype was estimated by a generalized linear model. Anaplasma phagocytophilum was identified by genetic typing in 274 I. ricinus ticks. The majority belonged to ecotype I (63.9%), 28.5% were ecotype II, and both ecotypes were identified in 7.7% of ticks. Ecotype II was more frequently identified in ticks originating from a site with presence of roe deer, whereas ecotype I was more frequent in adult ticks than in nymphs. Models taking into account the country-specific, site-specific, and habitat-specific aspects did not improve the goodness of the fit. Thus, roe deer presence in a certain site and the tick developmental stage are suggested to be the two factors consistently influencing the occurrence of a particular A. phagocytophilum ecotype in a positive I. ricinus tick.

Molecular detection of Anaplasma phagocytophilum in wild carnivores in north-eastern Poland

Background

Anaplasma phagocytophilum is an obligate parasitic intracellular bacterium. It is the causative agent of granulocytic anaplasmosis, with effects on human and animal health. In Europe, the pathogen is mainly transmitted among a wide range of vertebrate hosts by blood-sucking arthropods. The aim of this study was to determine the presence of A. phagocytophilum in wild carnivores, viz raccoon dogs (Nyctereutes procyonoides), badgers (Meles meles), foxes (Vulpes vulpes), martens (Martes sp.) and European polecats (Mustela putorius), using molecular methods.

Methods

In the present study, 174 spleen samples were collected from adult, wild carnivores hunted in the years 2013–2016. A short fragment (383 bp) of the 16S ribosomal RNA gene partial sequence was used as a marker to identify A. phagocytophilum in spleen samples collected from carnivores using nested PCR.

Results

The prevalence of A. phagocytophilum in wild carnivores was 31.61% (55/174). Seven sequences of A. phagocytophilum were generated from two raccoon dogs, two badgers, one marten, one red fox and one European polecat. Six identical nucleotide sequences were obtained from one raccoon dog, two badgers, one marten, one red fox and one European polecat (A. phagocytophilum sequences 1: MH328205–MH328209, MH328211), and these were identical to many A. phagocytophilum sequences in the GenBank database (100% similarity). The second sequence (A. phagocytophilum sequence 2: MH328210) obtained from the raccoon dog shared 99.74% identity with A. phagocytophilum sequence 1.

Conclusions

To our knowledge, this is the first study to use molecular methods to determine the presence of A. phagocytophilum in wild carnivores, viz raccoon dog, badger, marten and European polecat, in Poland. The detected A. phagocytophilum sequences (1 and 2) were closely related with those of A. phagocytophilum occurring in a wide range of wild and domestic animals and vectors.

Genetic characterization of Anaplasma phagocytophilum strains from goats (Capra aegagrus hircus) and water buffalo (Bubalus bubalis) by 16S rRNA gene, ankA gene and multilocus sequence typing

Anaplasma phagocytophilum is a Gram-negative obligate intracellular bacterium that replicates in neutrophil granulocytes. It is transmitted by ticks and causes tick-borne fever in domestic ruminants such as sheep, cattle and goats. However, in contrast to sheep and cattle little is known about the clinical course of infection in goats. We report here on three cases of symptomatic infection with A. phagocytophilum in two goats (Capra aegagrus hircus) and one water buffalo (Bubalus bubalis). The animals showed symptoms and laboratory findings similar to sheep and cattle. To our knowledge, this is the first report on the symptomatic infection of water buffalos with A. phagocytophilum. The infecting strains were genetically characterized by 16S rRNA gene, ankA gene and multilocus sequence typing (MLST). Four other strains from asymptomatically infected goats were also included. The ankA sequences from five goats were part of the formerly described ankA gene clusters I and IV that are known to contain A. phagocytophilum strains from sheep and cattle. However, the sequences from one goat and from the water buffalo belonged to ankA gene cluster II that was formerly described to be restricted to roe deer. A similar observation was made for MLST as three goats clustered with sequences from sheep and cattle, whereas three other goats and the water buffalo were found to be part of the roe deer cluster. However, since most of the strains from sheep and cattle were distinct from the roe deer strains, roe deer might not represent major reservoir hosts for tick-borne fever in domestic ruminants. When differing parts of the 16S rRNA gene were used for typing the results were conflicting. This shows that the use of a standardized typing method such as MLST is highly desirable to generate easily comparable results.

Anaplasma phagocytophilum evolves in geographical and biotic niches of vertebrates and ticks

Background

Anaplasma phagocytophilum is currently regarded as a single species. However, molecular studies indicate that it can be subdivided into ecotypes, each with distinct but overlapping transmission cycle. Here, we evaluate the interactions between and within clusters of haplotypes of the bacterium isolated from vertebrates and ticks, using phylogenetic and network-based methods.

Methods

The presence of A. phagocytophilum DNA was determined in ticks and vertebrate tissue samples. A fragment of the groEl gene was amplified and sequenced from qPCR-positive lysates. Additional groEl sequences from ticks and vertebrate reservoirs were obtained from GenBank and through literature searches, resulting in a dataset consisting of 1623 A. phagocytophilum field isolates. Phylogenetic analyses were used to infer clusters of haplotypes and to assess phylogenetic clustering of A. phagocytophilum in vertebrates or ticks. Network-based methods were used to resolve host-vector interactions and their relative importance in the segregating communities of haplotypes.

Results

Phylogenetic analyses resulted in 199 haplotypes within eight network-derived clusters, which were allocated to four ecotypes. The interactions of haplotypes between ticks, vertebrates and geographical origin, were visualized and quantified from networks. A high number of haplotypes were recorded in the tick Ixodes ricinus. Communities of A. phagocytophilum recorded from Korea, Japan, Far Eastern Russia, as well as those associated with rodents had no links with the larger set of isolates associated with I. ricinus, suggesting different evolutionary pressures. Rodents appeared to have a range of haplotypes associated with either Ixodes trianguliceps or Ixodes persulcatus and Ixodes pavlovskyi. Haplotypes found in rodents in Russia had low similarities with those recorded in rodents in other regions and shaped separate communities.

Conclusions

The groEl gene fragment of A. phagocytophilum provides information about spatial segregation and associations of haplotypes to particular vector-host interactions. Further research is needed to understand the circulation of this bacterium in the gap between Europe and Asia before the overview of the speciation features of this bacterium is complete. Environmental traits may also play a role in the evolution of A. phagocytophilum in ecotypes through yet unknown relationships.

Electronic supplementary material

The online version of this article (10.1186/s13071-019-3583-8) contains supplementary material, which is available to authorized users.

Simultaneous infection of cattle with different Anaplasma phagocytophilum variants

Anaplasma phagocytophilum is a tick-transmitted Gram-negative obligate intracellular bacterium that replicates in neutrophil granulocytes. It causes tick-borne fever in cattle and sheep. We report here the case of a 5-year-old cow from Germany with clinically overt granulocytic anaplasmosis presenting with fever, lower limb oedema and drop in milk-yield. The herd encompassed 10 animals, 8 other animals showed subclinical infection. The strains from the 9 A. phagocytophilum positive cows were molecularly characterized using ankA gene-based and multilocus sequence typing (MLST). Seven of 9 (78%) animals were infected simultaneously with different ankA variants belonging to ankA clusters I and IV. MLST analysis also revealed the presence of multiple strain types. This could be due to co-transmission or superinfection. Hosts harboring diverse A. phagocytophilum strains might enable the emergence of new ankA variants and/or MLST sequence types via bacterial recombination.

Diverse tick-borne microorganisms identified in free-living ungulates in Slovakia

BACKGROUND

Free-living ungulates are hosts of ixodid ticks and reservoirs of tick-borne microorganisms in central Europe and many regions around the world. Tissue samples and engorged ticks were obtained from roe deer, red deer, fallow deer, mouflon, and wild boar hunted in deciduous forests of south-western Slovakia. DNA isolated from these samples was screened for the presence of tick-borne microorganisms by PCR-based methods.

RESULTS

Ticks were found to infest all examined ungulate species. The principal infesting tick was Ixodes ricinus, identified on 90.4% of wildlife, and included all developmental stages. Larvae and nymphs of Haemaphysalis concinna were feeding on 9.6% of wildlife. Two specimens of Dermacentor reticulatus were also identified. Ungulates were positive for A. phagocytophilum and Theileria spp. Anaplasma phagocytophilum was found to infect 96.1% of cervids, 88.9% of mouflon, and 28.2% of wild boar, whereas Theileria spp. was detected only in cervids (94.6%). Importantly, a high rate of cervids (89%) showed mixed infections with both these microorganisms. In addition to A. phagocytophilum and Theileria spp., Rickettsia helvetica, R. monacensis, unidentified Rickettsia sp., Coxiella burnetii, "Candidatus Neoehrlichia mikurensis", Borrelia burgdorferi (s.l.) and Babesia venatorum were identified in engorged I. ricinus. Furthermore, A. phagocytophilum, Babesia spp. and Theileria spp. were detected in engorged H. concinna. Analysis of 16S rRNA and groEL gene sequences revealed the presence of five and two A. phagocytophilum variants, respectively, among which sequences identified in wild boar showed identity to the sequence of the causative agent of human granulocytic anaplasmosis (HGA). Phylogenetic analysis of Theileria 18S rRNA gene sequences amplified from cervids and engorged I. ricinus ticks segregated jointly with sequences of T. capreoli isolates into a moderately supported monophyletic clade.

CONCLUSIONS

The findings indicate that free-living ungulates are reservoirs for A. phagocytophilum and Theileria spp. and engorged ixodid ticks attached to ungulates are good sentinels for the presence of agents of public and veterinary concern. Further analyses of the A. phagocytophilum genetic variants and Theileria species and their associations with vector ticks and free-living ungulates are required.

A lifelong study of a pack Rhodesian ridgeback dogs reveals subclinical and clinical tick-borne Anaplasma phagocytophilum infections with possible reinfection or persistence

Background

Various tick-borne infections often occur without specific clinical signs and are therefore notoriously hard to diagnose separately in veterinary practice. Longitudinal studies over multiple tick seasons performing clinical, serological and molecular investigations in parallel, may elucidate the relationship between infection and disease. In this regard, six related Rhodesian Ridgeback dogs living as a pack became subject of lifetime studies due to ongoing tick infestations and recurring clinical problems. Blood samples for diagnostic tests were obtained throughout the years 2000 to 2009.

Methods

Data collected from clinical observations, hemograms, serology and detection of Anaplasma phagocytophilum, either by microscopy or by DNA amplification and typing, were placed in a time line. This dataset essentially presents as a prospective study enabling the association of the Anaplasma infections with occurring disease.

Results

All six dogs were infected, and two of them developed particular clinical symptoms that could be associated with Anaplasma infections over time. More specifically, episodes of general malaise with fever and purpura with thrombocytopenia and bacterial inclusions in granulocytes, were found concurrently with Anaplasma DNA and specific antibodies in peripheral blood samples. DNA from A. phagocytophilum variant 4 (of 16S rRNA) was found in multiple and sequential samples. DNA-sequences from variant 1 and the human granulocytic ehrlichiosis (HGE) agent were also detected.

Conclusions

In this study two lifelong cases of canine anaplasmosis (CGA) are presented. The data show that dogs can be naturally infected concurrently with A. phagocytophilum variant 1, variant 4 and the HGE agent. The ongoing presence of specific antibodies and Anaplasma DNA in one dog indicates one year of persisting infection. Treatment with doxycycline during recurring clinical episodes in the other dog resulted in transient clinical improvement and subsequent disappearance of specific antibodies and DNA suggesting that re-infection occurred.

Electronic supplementary material

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New records for Anaplasma phagocytophilum infection in small mammal species

Background

Tick-borne diseases pose a major threat in public health. The epidemiological dynamics of these diseases depends on the tick vector species and their hosts, as well as the geographical distribution and ecology of both. Among many possible hosts for ticks, small mammals have a major role in the development of immature stages of several tick species. Small mammals are also important reservoir hosts for several pathogenic agents and possible reservoirs for Anaplasma phagocytophilum. In this context, the aim of our study was to evaluate the prevalence of A. phagocytophilum in small mammal species in Romania.

Results

A total of 791 small mammals of 31 species were tested by PCR, targeting the rrs gene for detection of A. phagocytophilum DNA. Positive results were obtained in 20 small mammals: five Apodemus flavicollis (6.49%), three Sorex araneus (9.09%), three A. uralensis (4.84%), two A. sylvaticus (3.92%), and one of each Spermophilus cittelus (7.14%), Microtus agrestis (3.85%), Sorex minutus (3.85%), Muscardinus avellanarius (3.13%), Crocidura suaveolens (2.44%), Mus spicilegus (2%) and M. arvalis (1.75%).

Conclusions

Eleven small mammal species were found to be carriers of A. phagocytophilum, suggesting a possible involvement of these species in its epidemiology. To our knowledge, this is the first report of A. phagocytophilum in S. minutus, C. suaveolens, M. spicilegus, M. avellanarius and S. citellus.

Electronic supplementary material

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Co-circulation of different A. phagocytophilum variants within cattle herds and possible reservoir role for cattle

Background

Anaplasma phagocytophilum is a zoonotic tick-borne intracellular alpha-proteobacterium causing tick-borne fever, which leads to significant economic losses in domestic ruminants in Europe. Its epidemiological cycles are complex and reservoir host species of bovine strains have not yet been identified. Given that little genetic information is available on strains circulating within a defined bovine environment, our objective was to assess the genetic diversity of A. phagocytophilum obtained from the same farms over time.

Methods

Blood samplings were performed several times in two European herds. In the French herd, 169 EDTA-blood samples were obtained from 115 cows (32 were sampled two to four times). In the German herd, 20 cows were sampled six times (120 EDTA-blood samples). The presence of A. phagocytophilum DNA was assessed using a qPCR targeting msp2. The positive DNA samples underwent MLST at nine genetic markers (typA, ctrA, msp4, pleD, recG, polA, groEL, gyrA, and ankA). For each locus, sequences were aligned with available bacterial sequences derived from cattle, horse, dog, and roe deer hosts, and concatenated neighbor joining trees were constructed using three to six loci.

Results

Around 20% (57/289) of samples were positive. Forty positive samples from 23 French and six German cows (11 of them being positive at two time points) were sequenced. Six loci (typA, ctrA, msp4, pleD, recG, and polA) allowed to build concatenated phylogenetic trees, which led to two distinct groups of bovine variants in the French herd (hereafter called A and B), whereas only group A was detected in the German herd. In 42% of French samples, double chromatogram peaks were encountered in up to four loci. Eleven cows were found infected three weeks to 17 months after first sampling and harboured a new variant belonging to one or the other group.

Conclusions

Our results demonstrate the occurrence of two major bovine strain groups and the simultaneous infection of single cows by more than one A. phagocytophilum strain. This challenges the role of cattle as reservoirs for A. phagocytophilum. This role may be facilitated via long-term bacterial persistence in individual cows and active circulation at the herd scale.

Electronic supplementary material

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Epidemiology, genetic variants and clinical course of natural infections with Anaplasma phagocytophilum in a dairy cattle herd

Background

Anaplasma phagocytophilum is an obligate intracellular, tick-transmitted bacterium that causes granulocytic anaplasmosis in humans and several mammalian species including domestic ruminants where it is called tick-borne fever (TBF). Different genetic variants exist but their impact with regard to putative differences in host associations and pathogenicity are not yet completely understood.

Methods

Natural infections with A. phagocytophilum in a dairy cattle herd in Germany were investigated over one pasture season by using serology, haematology, blood chemistry and polymerase chain reaction (PCR). Sequence analysis of partial 16S rRNA, groEL, msp2 and msp4 genes of A. phagocytophilum was carried out in order to trace possible genetic variants and their relations between cattle, roe deer (Capreolus capreolus) and ticks (Ixodes ricinus) in this area.

Results

In total 533 samples from 58 cattle, 310 ticks, three roe deer and one wild boar were examined. Our results show (i) typical clinical symptoms of TBF in first-time infected heifers, such as high fever, reduced milk yield, lower limb oedema and typical haematological and biochemical findings such as severe leukopenia, erythropenia, neutropenia, lymphocytopenia, monocytopenia, a significant increase in creatinine and bilirubin and a significant decrease in serum albumin, γ-GT, GLDH, magnesium and calcium; (ii) a high overall prevalence of A. phagocytophilum infections in this herd as 78.9% (15/19) of the naïve heifers were real-time PCR-positive and 75.9% (44/58) of the entire herd seroconverted; and (iii) a high level of sequence variation in the analysed genes with five variants of the 16S rRNA gene, two variants of the groEL gene, three variants of the msp2 gene and four variants in the msp4 gene with certain combinations of these variants.

Conclusions

In cattle particular combinations of the genetic variants of A. phagocytophilum occurred, whereas three roe deer showed different variants altogether. This is indicative for a sympatric circulation of variants in this small geographical region (< 1 km²). Both re- and superinfections with A. phagocytophilum were observed in five cattle showing that infection does not result in sterile immunity. For prevention of clinical cases we suggest pasturing of young, not pregnant heifers to reduce economical losses.

Electronic supplementary material

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A 10-year surveillance of Rickettsiales (Rickettsia spp. and Anaplasma phagocytophilum) in the city of Hanover, Germany, reveals Rickettsia spp. as emerging pathogens in ticks

BACKGROUND

Rickettsiales (Rickettsia spp. and Anaplasma phagocytophilum) transmitted by ticks are considered (re-)emerging pathogens posing a risk to public health. Nevertheless, year-long monitoring studies on prevalences of these pathogens in questing ticks to contribute to public health risk assessment are rare.

METHODS

The current study extends previous prevalence surveillances (2005 and 2010) by 2015 to a 10-year monitoring. Therefore, 2100 questing Ixodes ricinus were collected from April to October 2015 at ten different recreation sites in the city of Hanover, Germany, to determine potential changes in tick infection rates with Rickettsiales.

RESULTS

Of the collected ticks, 288 were adult females, 285 adult males and 1527 nymphs. Overall, 3.8% (79/2100) of ticks were infected with A. phagocytophilum, 50.8% (1066/2100) with Rickettsia spp. and 2.2% (46/2100) with both pathogens. Statistical analyses revealed stagnating A. phagocytophilum infection rates over the 10-year monitoring period, whereas Rickettsia infections increased significantly (33.3% in 2005 and 26.2% in 2010 vs 50.8% in 2015). This increase was also characterized by prominent seasonality with higher prevalences from July to October.

CONCLUSIONS

As increased tick infection rates result in an increased risk for public health, the long-term data reported here provide significant implications for the understanding of progressing Rickettsiales distribution in ticks and essentially contribute to reliable public health risk assessments.

Host specificity, pathogen exposure, and superinfections impact the distribution of Anaplasma phagocytophilum genotypes in ticks, roe deer, and livestock in a fragmented agricultural landscape

Anaplasma phagocytophilum is a bacterial pathogen mainly transmitted by Ixodes ricinus ticks in Europe. It infects wild mammals, livestock, and, occasionally, humans. Roe deer are considered to be the major reservoir, but the genotypes they carry differ from those that are found in livestock and humans. Here, we investigated whether roe deer were the main source of the A. phagocytophilum genotypes circulating in questing I. ricinus nymphs in a fragmented agricultural landscape in France. First, we assessed pathogen prevalence in 1837 I. ricinus nymphs (sampled along georeferenced transects) and 79 roe deer. Prevalence was dramatically different between ticks and roe deer: 1.9% versus 76%, respectively. Second, using high-throughput amplicon sequencing, we characterized the diversity of the A. phagocytophilum genotypes found in 22 infected ticks and 60 infected roe deer; the aim was to determine the frequency of co-infections. Only 22.7% of infected ticks carried genotypes associated with roe deer. This finding fits with others suggesting that cattle density is the major factor explaining infected tick density. To explore epidemiological scenarios capable of explaining these patterns, we constructed compartmental models that focused on how A. phagocytophilum exposure and infection dynamics affected pathogen prevalence in roe deer. At the exposure levels predicted by the results of this study and the literature, the high prevalence in roe deer was only seen in the model in which superinfections could occur during all infection phases and when the probability of infection post exposure was above 0.43. We then interpreted these results from the perspective of livestock and human health.

Detecting and characterizing mixed infections with genetic variants of Anaplasma phagocytophilum in roe deer (Capreolus capreolus) by developing an ankA cluster-specific nested PCR

Background

Anaplasma phagocytophilum is a tick-transmitted Gram-negative obligate intracellular bacterium able to infect a wide variety of wild and domestic animals worldwide. Based on the genetic diversity observed with different molecular markers, several host-specific lineages have been identified. Roe deer is one of the most important reservoirs of this bacterium and hosts different genetic groups sometimes found on domestic animals. We therefore developed an ankA cluster-specific nested PCR (nPCR) to evaluate the prevalence of the three different ankA genetic groups described in roe deer (clusters II, III and IV) at three locations in France and the level of co-infections.

Results

The specificity of the three nPCRs was assessed by partially sequencing 35 amplicons of ankA genes obtained from the different nested PCRs. All three genetic lineages were detected in roe deer from all three geographical locations. Of the infected deer population, 60.7% were co-infected by two or three different genetic variants. Co-infections varied from 42.9 to 70.6% of the infected population depending on the local infection prevalences (from 33.3 to 73.9%). All types of mixed infections occurred, suggesting the absence of a strict variant exclusion by another variant.

Conclusions

Mixed infections by two or three genetic variants of A. phagocytopilum are a common feature in roe deer. Genetic variants (cluster IV) also found in domestic ruminants (cattle and sheep) were present in all the roe deer populations analyzed, suggesting a shared epidemiological cycle.

Electronic supplementary material

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Guidelines for the Direct Detection of Anaplasma spp. in Diagnosis and Epidemiological Studies

The genus Anaplasma (Rickettsiales: Anaplasmataceae) comprises obligate intracellular Gram-negative bacteria that are mainly transmitted by ticks, and currently includes six species: Anaplasma bovis, Anaplasma centrale, Anaplasma marginale, Anaplasma phagocytophilum, Anaplasma platys, and Anaplasma ovis. These have long been known as etiological agents of veterinary diseases that affect domestic and wild animals worldwide. A zoonotic role has been recognized for A. phagocytophilum, but other species can also be pathogenic for humans. Anaplasma infections are usually challenging to diagnose, clinically presenting with nonspecific symptoms that vary greatly depending on the agent involved, the affected host, and other factors such as immune status and coinfections. The substantial economic impact associated with livestock infection and the growing number of human cases along with the risk of transfusion-transmitted infections, determines the need for accurate laboratory tests. Because hosts are usually seronegative in the initial phase of infection and serological cross-reactions with several Anaplasma species are observed after seroconversion, direct tests are the best approach for both case definition and epidemiological studies. Blood samples are routinely used for Anaplasma spp. screening, but in persistently infected animals with intermittent or low-level bacteremia, other tissues might be useful. These guidelines have been developed as a direct outcome of the COST action TD1303 EURNEGVEC ("European Network of Neglected Vectors and Vector-Borne Diseases"). They review the direct laboratory tests (microscopy, nucleic acid-based detection and in vitro isolation) currently used for Anaplasma detection in ticks and vertebrates and their application.